Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. Also, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV) and hybrid electric vehicles (HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuel.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle- or large-sized devices, such as vehicles, use a middle- or large-sized battery module having a plurality of battery cells electrically connected with each other because high power and large capacity are necessary for the middle- or large-sized devices.
Preferably, the middle- or large-sized battery module is manufactured with small size and weight if possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of the middle- or large-sized battery module. Especially, much interest is currently generated in the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the weight of the pouch-shaped battery is small and the manufacturing costs of the pouch-shaped battery are low.
However, when a middle- or large-sized battery module is constructed using a plurality of battery cells or a plurality of unit modules each of which includes a predetermined number of battery cells, a plurality of members are generally needed to mount the battery cells or the unit modules in a middle- or large-sized battery module case and to mechanically couple the middle- or large-sized battery module case to a mounting member, such as a body frame, of a vehicle, and, as a result, a process for assembling the members is very complicated. Furthermore, there is needed a space for coupling the members, with the result that the total size of the system is increased. The increase in size of the system is not preferred in the above-described aspect. Consequently, there is a high necessity for a middle- or large-sized battery module having a joint structure that is more compact and structurally stable.
In this connection, there are disclosed some technologies on a joint structure of a middle- or large-sized battery module mounting frame for mounting a middle- or large-sized battery module, having unit modules mounted therein, to a predetermined region of a vehicle.
For example, Japanese Patent Registration No. 3324182 discloses a joint structure of a battery mounting frame wherein bolts, inserted from the bottom of a floor panel of a vehicle, joined to guide tubes and nut plates such that a lattice-shaped battery frame, in which a plurality of batteries are received, is mounted at the bottom of the floor panel of the vehicle.
However, the above-described technology has a problem in that the joint structure is formed only at one side of the battery frame, with the result that the batteries are spaced apart from the battery frame, and therefore, when impacts, such as vibrations, are applied to joint structure from the vehicle, the joint structure is not structurally stable. Also, the above-described technology has a problem in that the joint structure includes a plurality of joint members, with the result that the manufacturing costs are increased, and the assembly process to mount the battery frame to the floor panel of the vehicle is not easily performed.